1. Field of the Invention
The present invention relates to a wireless communication system. More particularly, the present invention relates to a method and an apparatus for transmitting beam information in a wireless communication system.
2. Description of the Related Art
Wireless communication systems are developing to support a higher data rate, in order to satisfy the demand for the continuously increasing wireless data traffic. Fourth Generation (4G) systems, which have started to be commercialized, are being developed mainly towards the improvement of frequency spectral efficiency in order to increase the data rate. However, only the improvement of frequency spectral efficiency is insufficient to satisfy the explosively increasing requirements for the wireless data traffic.
Schemes for addressing such a problem include a scheme using a very wide frequency band. In related-art wireless communication systems (for example, a mobile communication cellular system), a frequency band of 10 or less GHz is usually used and it is very difficult to secure a wide frequency band. Therefore, a related-art wireless communication system secures a wideband frequency of a higher frequency band.
However, the higher the frequency for wireless communication, the larger the path loss of an electric wave. Further, as the path loss of an electric wave increases, the distance the electric wave reaches decreases, to thereby reduce the service coverage area. In order to address this problem, a beam forming technology has been used as a technology for reducing the path loss of an electric wave and increasing the distance the electric wave reaches.
The beam forming includes a transmission beam forming performed on the transmitter side and a reception beam forming performed on the receiver side. Transmission beam forming is a technology of concentrating the arrival area of the electric wave in a particular direction by using a plurality of antennas. Here, an aggregation of the plurality of antennas is referred to as an antenna array and each antenna included in the antenna array is referred to as an array element. The antenna array may be configured in various forms including a linear array, a planar array, etc. Use of the transmission beam forming increases the directivity of a signal, so as to increase the distance by which the signal is transmitted. Moreover, when the transmission beam forming is used, nearly no signals are transmitted in other directions than an oriented direction, which results in a large reduction of signal interference to other receivers.
Meanwhile, the receiver side performs beam forming for an incoming signal by using a reception antenna array. The reception beam forming concentrates the incoming electric wave in a particular direction to thereby increase the sensitivity of the signal received in the particular direction while preventing reception of incoming signals in the other directions to thereby intercept the interference signals.
The beam forming requires a beam selection technology which enables each of a base station and a mobile station to exactly measure a transmission beam and a reception beam and report the most proper beams for communication. However, an obstruction in a link between the base station and the mobile station or a movement of the mobile station may cause a momentary beam change, which may cause a mismatch between reported beam information and information of a proper beam at the time point of transmission of a current signal, to thereby largely deteriorate the performance. Therefore, the related-art wireless communication systems have required a scheme capable of addressing the problem which may be caused by a mismatch in the beam information exchanged between a base station and a mobile station according to a beam change.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.